电刷镀镍钢-铝钎焊接头的界面组织与力学性能

Interface Microstructure and Mechanical Property of Nickel Brush Plating Steel-aluminum Brazed Joint

针对因界面形成脆性金属间化合物IMC而导致钢/铝钎焊接头力学性能差的问题,进行了Q235表面电刷镀镍预处理、及随后采用Al-12.6Si-15Cu-2Ni钎料的Q235/1060炉中钎焊试验研究。结果表明,适当厚度的电刷镀镍层能够有效提高钢/铝钎焊接头的强度和韧性,电刷镀时间15 min试件的钎焊接头具有最大的剪切强度(≈95 MPa),比未电刷镀试件(≈56 MPa)提高近70%;剪切断口中韧性断裂面积约占40%,比未电刷镀试件(≈10%)增加了4倍。电刷镀镍钢/铝钎焊接头中外侧IMC(Fe2Al5相)层的厚度变薄,内侧IMC(Fe Al3相)的形态由羽毛状边缘变成较为平直光滑的边缘。钢表面电刷镀镍对钎焊过程中液固界面反应的抑制和调制作用是其提高钢/铝钎焊接头力学性能的主要原因。

Aiming at solving the problem of poor mechanical properties of brazed joint of steel/aluminum due to the formation of the interface forming brittle intermetallic compounds（IMCs）, the nickel brush-plating on the surface of Q235 and followed by furnace brazing to 1060 Al alloy with Al-12.6Si-15Cu-2Ni as filler materials was studied. The results show that both shear strength and ductility of steel/aluminum brazed joint increase by a suitable thickness layer of surface of the steel.The shear strength of the specimen brush plated for 15 min is 95 MPa, increased by about 70% than nickel brush plating on the non-brush-plating one（≈56MPa）. The toughness area in shearing section is about 40%, increased by about 4 times higher than that of non-brush-plating one（≈10%）. In the nickel brush plating steel/aluminum brazed joint, the outside IMC（Fe2Al5）gets thinner and the shape of inside IMC（Fe Al3） changes from feathery to smooth flat. The improvement in mechanical property may be ascribed to the suppression and the modulation effects of nickel brush plating on the interface reactions during brazing process.